This invention relates to digital thermostats powered solely by battery means, and particularly to an improved means therein for indicating a low battery voltage condition.
In digital thermostats powered solely by battery means, it is necessary that the batteries (or battery) be replaced before the battery voltage drops to a value insufficient to enable proper operation of the thermostat. While it is recommended that the batteries be replaced at specific intervals so as to minimize the possibility of the occurrence of such a voltage condition, it is believed that such recommendations are typically ignored. Accordingly, it is deemed necessary to provide some means for indicating to the thermostat user that the battery voltage is approaching such a value.
One requirement of such indicating means is that it be activated a sufficient time before the battery voltage drops to a value insufficient to enable proper operation of the thermostat so as to provide ample time for the user to purchase and install new batteries. Another requirement is that it readily attract the attention of the user. Another requirement is that it not result in the use of more electrical energy than is used in normal thermostat operation, which additional energy use would shorten the remaining life of the batteries. Yet another requirement is that it be relatively inexpensive.